The present invention relates generally to integrated lancing and analytical devices and more particularly to a novel integrated lancing and analytical device.
There are many medical conditions which require frequent measurement of the concentration of a particular analyte in the blood of a patient. For example, diabetes is a disease which typically requires a patient to routinely measure the concentration of glucose in his/her blood. Based upon the results of each blood glucose measurement, the patient may then require a particular drug treatment (e.g., an injection of insulin) in order to regulate that the blood glucose level of the patient remains within a specified range. Exceeding the upper limit of said range (hyperglycemia) or dropping beneath the lower limit of said range (hypoglycemia) should be avoided with as much diligence as possible to prevent the patient from experiencing serious medical complications which include, inter alia, retinopathy, nephropathy, and neuropathy.
A multi-step process is commonly practiced by diabetes patients to self-monitor the level of glucose present in their blood.
In the first step of said process, a patient is required to provide a blood sample suitable for testing. Blood samples taken from a patient for blood sugar monitoring are typically obtained by piercing the skin of the patient using a lancet device. A lancet device typically includes a body and a lancet. The body is typically adapted to be held by the user, the lancet being coupled to the body and being adapted to penetrate through the epidermis (the outermost layer of the skin) of the patient and into the dermis (the layer of skin directly beneath the epidermis) which is replete with capillary beds. The puncture of one or more capillaries by the lancet generates a sample of blood which exits through the incision in the patient's skin.
In some lancet devices, the lancet extends from the body at all times. In other lancet devices, the lancet is adapted to be moved, when actuated, from a retracted position in which the lancet tip is disposed within the body to an extended position in which the lancet tip extends beyond the body. Typically, the movement of the lancet from its retracted position to its extended position is effected with such force that contact of the moving lancet tip with the skin of a patient results in the piercing of the skin of the patient. In many such lancet devices having a movable lancet, the lancet is automatically drawn back into the body after reaching its extended position in order to minimize the risk of inadvertent lancet sticks.
In the second step of said process, a blood glucose monitoring system is utilized to measure the concentration of glucose in the blood sample. One type of glucose monitoring system which is well known and widely used in the art includes a blood glucose meter (also commonly referred to a blood glucose monitor) and a plurality of individual, disposable, electrochemical test strips which can be removably loaded into the meter. Examples of blood glucose monitoring systems of the type described above are manufactured and sold by Abbott Laboratories, Medisense Products of Bedford, Mass. under the PRECISION line of blood glucose monitoring systems.
Each individual electrochemical test strip typically includes a substrate which is formed as a thin, rectangular strip of non-conductive material, such as plastic. A plurality of carbon-layer electrodes are deposited on the substrate along a portion of its length in a spaced apart relationship, one electrode serving as the reference electrode for the test strip and another electrode serving as the working electrode for the test strip. All of the conductive electrodes terminate at one end to form a reaction area for the test strip. In the reaction area, an enzyme is deposited on the working electrode. When exposed to the enzyme, glucose present in a blood sample undergoes a chemical reaction which produces a measurable electrical response. The other ends of the electrical contacts are disposed to electrically contact associated conductors located in the blood glucose monitor, as will be described further below.
A blood glucose monitor is typically modular and portable in construction to facilitate its frequent handling by the patient. A blood glucose monitor often comprises a multi-function test port which is adapted to receive the test strip in such a manner so that an electrical communication path is established therebetween. As such, an electrical reaction created by depositing a blood sample onto the reaction area of the test strip travels along the working electrode of the test strip and into the test port of the blood glucose monitor. Within the housing of the monitor, the test port is electrically connected to a microprocessor which controls the basic operations of the monitor. The microprocessor, in turn, is electrically connected to a memory device which is capable of storing a multiplicity of blood glucose test results.
In use, the blood glucose monitoring system of the type described above can be used in the following manner to measure the glucose level of a blood sample and, in turn, store the result of said measurement into memory as test data. Specifically, a disposable test strip is unwrapped from its packaging and is inserted into the test port of the monitor. With the test strip properly inserted into the monitor, there is established a direct electrical contact between the conductors on the test strip and the conductors contained within the test port, thereby establishing an electrical communication path between the test strip and the monitor. Having properly disposed the test strip into the test port, the monitor typically displays a “ready” indication on its display.
The user is then required to provide a blood sample using a lancing device. Specifically, a disposable lancet is unwrapped from its protective packaging and is loaded into a corresponding lancing device. The lancing device is then loaded, if necessary, and fired into the skin of the patient to provide a blood sample.
After lancing the skin, the patient is required to deposit one or more drops of blood from the patient's wound site onto the reaction area of the test strip. When a sufficient quantity of blood is deposited on the reaction area of the test strip, an electrochemical reaction occurs between the blood sample and the enzyme deposited on the working electrode which, in turn, produces an electrical current which decays exponentially over time. The decaying electrical current created through the chemical reaction between the enzyme and the glucose molecules in the blood sample, in turn, travels along the electrically conductive path established between the test strip and the monitor and is measured by the microprocessor of the monitor. The microprocessor of the monitor, in turn, correlates the declining current to a standard numerical glucose value (e.g., using a scaling factor). The numerical glucose value calculated by the monitor is then shown on the monitor display for the patient to observe. In addition, the data associated with the particular blood glucose measurement is stored into the memory for the monitor.
A principal drawback associated with diabetes management systems of the type described above is that the lancing and glucose measurement operations are performed independently of one another. As a result, the user is required to possess both a lancet device and a blood glucose test monitor (as well as an individually packaged lancet and test strip) in order to perform a single assay. Furthermore, because the lancing and glucose measurement operations are performed independently of one another, the aforementioned process for performing an assay is relatively complicated and requires a considerably high level of manual dexterity, which is highly undesirable.
Accordingly, some diabetes management systems presently available in the market include a single blood glucose test monitor which is capable of performing both the lancing and glucose measurement operations. One type of glucose monitoring system which includes a single meter for performing both the lancing and glucose measurement operations is manufactured and sold by Abbott Laboratories, Medisense Products of Bedford, Mass. under the SOF•TACR™ line of diabetes management systems. The SOF•TACT™ blood glucose meter is represented, inter alia, in U.S. Pat. No. 6,506,168, which is incorporated herein by reference.
The SOF•TACT™ blood glucose meter is adapted to receive both a single disposable lancet and a single disposable test strip. In order to prepare the meter for an assay, the patient is required to open a pivotally mounted cover. With the cover opened, the patient is required to unwrap an individually sealed lancet and, in turn, mount the unwrapped lancet in a cylindrical lancet holder. In addition, the patient is required to unwrap an individually sealed test strip and, in turn, insert the unwrapped test strip into a test strip port. With a lancet and a test strip installed into the meter as described above, the cover is pivoted closed. To commence an assay, the patient positions a specified region of the monitor against his/her skin and presses an activation button. Depression of the activation button creates a pressure gradient which drives the lancet through an opening in the pivotable cover and into the patient's skin. The pressure gradient is then removed which retracts the lancet to its original unfired position.
After an opening has been formed in the skin of the patient, the blood sample is collected so that an assay can be performed. Specifically, a vacuum pump is used to draw blood from the wound site and in the direction towards the test strip. Simultaneously, mechanical linkages within the monitor use pressure to move the test strip towards the opening in the pivotable cover such that blood emerging from the patient's skin collects onto the reaction area of the test strip. When a sufficient amount of blood has been collected, the vacuum pump is deactivated. The meter then performs the assay based upon the electrochemical signal generated by the test strip and displays the result on an LCD screen.
Upon completion of the assay, the user is required to pivot open the cover of the meter and remove the used test strip and lancet. Because each test strip and lancet is designed for a single-use, the used test strip and lancet are discarded. The cover is then closed until future tests are required, at which time, the above-described process is repeated.
Although the SOF•TACT™ meter effectively combines both lancing and measurement processes into a single system, the user is still required to store and use two separate disposable products (i.e., a lancet and a test strip) in order to perform a single assay. As can be appreciated, the requirement that the user store, unwrap, load and discard two separate disposable items renders the system still somewhat complex to use.
Accordingly, some diabetes management systems which are known in the art require only the following two items in order to complete a blood glucose test: (1) a single blood glucose test monitor capable of performing both the lancing and glucose measurement operations and (2) an integrated, disposable, single-use test cartridge which includes both the lancing and analytical components (said cartridge being commonly referred to in the art as an integrated lancing and analytical device or simply as an integrated disposable).
As an example of an integrated lancing and analytical device, in U.S. Pat. No. 6,071,294 there is disclosed a cartridge for sampling and analyzing blood from the skin of a patient. The cartridge has a cartridge case, a lancet, and associated with the cartridge case an analytical region for analyzing the property of blood. The lancet has a tip for lancing the skin and is housed in the cartridge case. The lancet is operatively connected to the cartridge case such that the lancet can be pushed to extend its tip outside the cartridge case for lancing the skin to yield blood. The blood from the lancing wound is transferred to the analytical region and is analyzed.
As can be appreciated, the principal benefit of a system which uses integrated lancing and analytical devices is the simplicity in which a patient can perform an assay. Specifically, a patient is required only to unwrap and load a single cartridge into a corresponding meter prior to performing the assay. When an assay is required, the user is only required to place his/her finger against a region of the cartridge and, subsequent thereto, depress a suitable trigger or button. As a result, the number and relatively complexity of steps which the patient is required to perform is significantly reduced, which is highly desirable.
However, it should be noted that conventional integrated lancing and analytical devices suffer from a notable drawback. Specifically, blood glucose monitoring systems which use integrated disposable cartridges of the type described above typically include no means for drawing the blood sample from the wound site after lancing and, in turn, directing the drawn blood sample to the reaction area of the test strip. Rather, these systems typically require the user to manually expresses blood from his/her finger (e.g., by squeezing or massaging the skin surrounding the wound site). The user then orientates his/her finger such that the expressed blood droplets collect on the reaction area of the test strip. It should be noted that, because these systems include no means for expressing blood from the wound site and, in turn, directing the expressed blood to the reaction area of the test strip, a larger blood sample is often required from the patient, thereby increasing the overall level of discomfort experienced by the patient.